When your SmartConsole session is dead...

it will show you this scary message:

One reason for that is network connection to management server was temporarily interrupted. Like for example when you install or uninstall CheckPoint Identity Agent that disconnects your network interface without even notifying you first to save your work/sessions (good usability as usual ).

Anyway, do not poke TAC just yet, try to restart console first. That will likely make it work again.